A wind turbine for wind turbine generator has been used. FIG. 1 shows an example of a configuration of the wind turbine. A tower 2 is fixed vertical to the ground. A nacelle 3 is supported on the tower 2. A hub 5 is rotatably supported by the nacelle 3 in a horizontal direction via a main shaft 4. The hub 5 is covered with a cover 6. Blades 7 are attached to the hub 5.
At power wind generation, the pitch angle of the blade 7 is controlled so as to efficiently convert wind power to torque. When the blade 7 receives wind, the main shaft 4 rotates. The rotation is accelerated by a gear box 8. The accelerated rotation causes a generator 9 to generate electric power.
Patent Document 1 is cited as a reference technique relating to the configuration of a hub.